Suturing or stitching of tissue is performed in surgical procedures or other cases where closing of incisions or cuts is required. Suturing is usually performed by grasping the tissue to be sutured, pushing a first end of a needle having a needle tip through one side of the tissue and then grasping the needle tip from the other side of the tissue to pull the needle through. The needle and a suture attached to a second end of the needle are then pulled through the tissue and the suture is tied.
Suturing is a simple procedure when it is performed on external tissues because the needle and suture can be easily manipulated. However, in endoscopic or other minimally invasive surgical procedures that require suturing of internal tissues access to the suturing area is limited and this limits the ability to manipulate the needle and suture.
Various types of endoscopic surgical instruments are known in the art that allow suturing and stitching of internal tissues during endoscopic surgical procedures. These instruments generally include a slender tube containing a push rod which is axially movable within the tube by means of a manual actuator. An end effector is coupled to a distal end of the tube and the push rod so that axial movement of the push rod is translated to rotational or pivotal movement of the end effector. Referring to FIG. 4, an end effector 122 that allows suturing of internal tissue usually includes an upper jaw 124 and a lower jaw 126 that grasp the soft tissue and at a predetermined minimum distance between the upper and lower jaw deploy a needle and a suture 128. The needle and suture 128 are pushed from the lower jaw 126 to the upper jaw 124, where the upper jaw captures them and pulls them through the soft tissue. In this prior art suturing devices there is no control of the distance between the upper and lower jaw and of the timing when the needle is deployed. As a result, in some cases, the needle is deployed prematurely, i.e., the needle is engaged in tissue, but not captured by the upper jaw. When premature needle deployment occurs, the suturing action needs to be repeated. Multiple premature needle deployments may results in soft tissue damage. Another problem of premature deployment is that it is difficult to back the needle out once it is into tissue but cannot be captured on the other side. Accordingly there is a need to prevent premature needle deployment in endoscopic suturing devices that utilize a jaw-type end effector for needle manipulation during endoscopic suturing procedures.